Helix-Turn-Helix DNA binding domain of the transcription regulators MlrA and CarA; Helix-turn-helix (HTH) transcription regulator MlrA (merR-like regulator A), N-terminal domain. The MlrA protein, also known as YehV, has been shown to control cell-cell aggregation by co-regulating the expression of curli and extracellular matrix production in Escherichia coli and Salmonella typhimurium. Its close homolog, CarA from Myxococcus xanthus, is involved in activation of the carotenoid biosynthesis genes by light. These proteins belong to the MerR superfamily of transcription regulators that promote expression of several stress regulon genes by reconfiguring the spacer between the -35 and -10 promoter elements. Their conserved N-terminal domains contain predicted HTH motifs that mediate DNA binding, while the dissimilar C-terminal domains bind specific coactivator molecules. Many MlrA- and CarA-like proteins in this group appear to lack the long dimerization helix seen in the N-terminal domains of typical MerR-like proteins.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 496082568   3 YSIGEFARLCGINATTLRAWQRRYGLLKPLRTDGGHRQYSDDDVQQALKILDWVKKGVPVSQVKPLLS 70
Cdd:cd01104    1 YTIGAVARLTGVSPDTLRAWERRYGLPAPQRTDGGHRLYSEADVARLRLIRRLTSEGVRISQAAALAL 68

DNA-binding transcriptional regulator, MerR family [Transcription];

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 496082568   5 IGEFARLCGINATTLRAWQRrYGLLKPL-RTDGGHRQYSDDDVQQALKILDWVKKGVPVSQVKPLLSRPGARRTnNWLTL 83
Cdd:COG0789    1 IGEVARLTGVSVRTLRYYER-IGLLPPPeRTEGGYRLYSEEDVERLRFIRRLRELGFSLAEIRELLDLLDDGEE-EVREL 78

                         90       100
                 ....*....|....*....|
gi 496082568  84 QETMLQRLKEgKIESLRQLI 103
Cdd:COG0789   79 LEEHLAELEA-QIAELQALR 97

Helix-Turn-Helix DNA binding domain of the transcription regulators MlrA and CarA; Helix-turn-helix (HTH) transcription regulator MlrA (merR-like regulator A), N-terminal domain. The MlrA protein, also known as YehV, has been shown to control cell-cell aggregation by co-regulating the expression of curli and extracellular matrix production in Escherichia coli and Salmonella typhimurium. Its close homolog, CarA from Myxococcus xanthus, is involved in activation of the carotenoid biosynthesis genes by light. These proteins belong to the MerR superfamily of transcription regulators that promote expression of several stress regulon genes by reconfiguring the spacer between the -35 and -10 promoter elements. Their conserved N-terminal domains contain predicted HTH motifs that mediate DNA binding, while the dissimilar C-terminal domains bind specific coactivator molecules. Many MlrA- and CarA-like proteins in this group appear to lack the long dimerization helix seen in the N-terminal domains of typical MerR-like proteins.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 496082568   3 YSIGEFARLCGINATTLRAWQRRYGLLKPLRTDGGHRQYSDDDVQQALKILDWVKKGVPVSQVKPLLS 70
Cdd:cd01104    1 YTIGAVARLTGVSPDTLRAWERRYGLPAPQRTDGGHRLYSEADVARLRLIRRLTSEGVRISQAAALAL 68

helix_turn_helix, mercury resistance;

                           10        20        30        40        50        60        70
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|.
gi 496082568     3 YSIGEFARLCGINATTLRAWQRrYGLLKP-LRTDGGHRQYSDDDVQQALKILDWVKKGVPVSQVKPLLSRP 72
Cdd:smart00422   1 YTIGEVAKLAGVSVRTLRYYER-IGLLPPpIRTEGGYRLYSDEDLERLRFIKRLKELGFSLEEIKELLELL 70

Helix-Turn-Helix DNA binding domain of MerR-like transcription regulators; Helix-turn-helix (HTH) MerR-like transcription regulator, N-terminal domain. The MerR family transcription regulators have been shown to mediate responses to stress including exposure to heavy metals, drugs, or oxygen radicals in eubacterial and some archaeal species. They regulate transcription of multidrug/metal ion transporter genes and oxidative stress regulons by reconfiguring the spacer between the -35 and -10 promoter elements. A typical MerR regulator is comprised of two distinct domains that harbor the regulatory (effector-binding) site and the active (DNA-binding) site. Their N-terminal domains are homologous and contain a DNA-binding winged HTH motif, while the C-terminal domains are often dissimilar and bind specific coactivator molecules such as metal ions, drugs, and organic substrates.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 496082568   3 YSIGEFARLCGINATTLRAWQRRyGLLKPLRTDGGHRQYSDDDVQQALKILDWVKKGVPVSQVKPLLsrpGARRTNNWLT 82
Cdd:cd00592    1 YTIGEVAKLLGVSVRTLRYYEEK-GLLPPERSENGYRLYSEEDLERLRLIRRLRELGLSLKEIRELL---DARDEELSLA 76

                         90       100
                 ....*....|....*....|....
gi 496082568  83 LQETMLQRLK---EGKIESLRQLI 103
Cdd:cd00592   77 ALLALLDEKLaelEEKIARLEALL 100

Helix-Turn-Helix DNA binding domain of transcription regulators from the MerR superfamily; Helix-turn-helix (HTH) transcription regulator MerR superfamily, N-terminal domain. The MerR family transcription regulators have been shown to mediate responses to stress including exposure to heavy metals, drugs, or oxygen radicals in eubacterial and some archaeal species. They regulate transcription of multidrug/metal ion transporter genes and oxidative stress regulons by reconfiguring the spacer between the -35 and -10 promoter elements. A typical MerR regulator is comprised of two distinct domains that harbor the regulatory (effector-binding) site and the active (DNA-binding) site. Their N-terminal domains are homologous and contain a DNA-binding winged HTH motif, while the C-terminal domains are often dissimilar and bind specific coactivator molecules such as metal ions, drugs, and organic substrates.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|
gi 496082568   3 YSIGEFARLCGINATTLRAWQRRyGLLKPLRTDGGHRQYSDDDVQQALKI 52
Cdd:cd04761    1 YTIGELAKLTGVSPSTLRYYERI-GLLSPARTEGGYRLYSDADLERLRLI 49

Helix-Turn-Helix DNA binding domain of the BmrR transcription regulator; Helix-turn-helix (HTH) multidrug-efflux transporter transcription regulator, BmrR and YdfL of Bacillus subtilis, and related proteins; N-terminal domain. Bmr is a membrane protein which causes the efflux of a variety of toxic substances and antibiotics. BmrR is comprised of two distinct domains that harbor a regulatory (effector-binding) site and an active (DNA-binding) site. The conserved N-terminal domain contains a winged HTH motif that mediates DNA binding, while the C-terminal domain binds coactivating, toxic compounds. BmrR shares the N-terminal DNA binding domain with other transcription regulators of the MerR superfamily that promote transcription by reconfiguring the spacer between the -35 and -10 promoter elements.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 496082568   3 YSIGEFARLCGINATTLrawqRRY---GLLKPLRTDG--GHRQYSDDDVQQALKILDWVKKGVPVSQVKPLLSRPGARRT 77
Cdd:cd01107    1 FTIGEFAKLSNLSIKAL----RYYdkiGLLKPAYVDPdtGYRYYSAEQLERLNRIKYLRDLGFPLEEIKEILDADNDDEL 76

                         90       100
                 ....*....|....*....|....*.
gi 496082568  78 NNWLTLQETMLQRlkegKIESLRQLI 103
Cdd:cd01107   77 RKLLREKLAELEA----EIEELQRIL 98

Helix-Turn-Helix DNA binding domain of putative Cfa-like transcription regulators; Putative helix-turn-helix (HTH) MerR-like transcription regulator; conserved, Cfa-like, unknown proteins (~172 a.a.). The N-terminal domain of these proteins appears to be related to the HTH domain of Cfa, a cyclopropane fatty acid synthase. These Cfa-like proteins have a unique C-terminal domain with conserved histidines (motif HXXFX7HXXF). Based on sequence similarity of the N-terminal domains, these proteins are predicted to function as transcription regulators that mediate responses to stress in eubacteria. They belong to the MerR superfamily of transcription regulators that promote transcription of various stress regulons by reconfiguring the operator sequence located between the -35 and -10 promoter elements. A typical MerR regulator is comprised of distinct domains that harbor the regulatory (effector-binding) site and the active (DNA-binding) site. Their N-terminal domains are homologous and contain a DNA-binding winged HTH motif, while the C-terminal domains are often dissimilar and bind specific coactivator molecules such as metal ions, drugs, and organic substrates.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 496082568   3 YSIGEFARLCGINATTLRAWQRRyGLLKP-LRTDGGHRQYSDDDVQQALKILDWVKKGVPVSQVKPLLSRPGARRTnnwL 81
Cdd:cd04790    2 LTISQLARQFGLSRSTLLYYERI-GLLSPsARSESNYRLYGERDLERLEQICAYRSAGVSLEDIRSLLQQPGDDAT---D 77

                         90       100
                 ....*....|....*....|
gi 496082568  82 TLQETMLQRLKEgkIESLRQ 101
Cdd:cd04790   78 VLRRRLAELNRE--IQRLRQ 95

Helix-Turn-Helix DNA binding domain of putative MlrA-like transcription regulators; Putative helix-turn-helix (HTH) MlrA-like transcription regulators (subgroup 2), N-terminal domain. The MlrA protein, also known as YehV, has been shown to control cell-cell aggregation by co-regulating the expression of curli and extracellular matrix production in Escherichia coli and Salmonella typhimurium. These proteins belong to the MerR superfamily of transcription regulators that promote expression of several stress regulon genes by reconfiguring the spacer between the -35 and -10 promoter elements. Their conserved N-terminal domains contain predicted HTH motifs that mediate DNA binding, while the dissimilar C-terminal domains bind specific coactivator molecules.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 496082568   3 YSIGEFARLCGINATTLRAWQRRYGLLKPLRTDGGHRQYSDDDVQQALKILDWVK-KGvpvsqvkplLSRPGARrtnnwl 81
Cdd:cd04765    1 FSIGEVAEILGLPPHVLRYWETEFPQLKPVKRAGGRRYYRPKDVELLLLIKHLLYeKG---------YTIEGAK------ 65

                         90       100       110
                 ....*....|....*....|....*....|....*
gi 496082568  82 tlqetmlQRLKEGKIESLRQLIYDAGREYPRQELV 116
Cdd:cd04765   66 -------QALKEDGAAAIREEEAEERLPSIRAELL 93

Helix-Turn-Helix DNA binding domain of the MerR1 transcription regulator; Helix-turn-helix (HTH) transcription regulator MerR1. MerR1 transcription regulators, such as Tn21 MerR and Tn501 MerR, mediate response to mercury exposure in eubacteria. These proteins are comprised of distinct domains that harbor the regulatory (effector-binding) site and the active (DNA-binding) site. Their conserved N-terminal domains contain winged HTH motifs that mediate DNA binding, while the C-terminal domains have three conserved cysteines that define a mercury binding site. These proteins share the N-terminal DNA binding domain with other transcription regulators of the MerR superfamily that promote transcription by reconfiguring the spacer between the -35 and -10 promoter elements.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 496082568   3 YSIGEFARLCGINATTLRAWQRRyGLL-KPLRTDGGHRQYSDDDVQqalkILDWVKK----GVPVSQVKPLLS--RPGAR 75
Cdd:cd04783    1 LTIGELAKAAGVNVETIRYYQRR-GLLpEPPRPEGGYRRYPEETVT----RLRFIKRaqelGFTLDEIAELLEldDGTDC 75

                         90       100       110       120       130       140
                 ....*....|....*....|....*....|....*....|....*....|....*....|..
gi 496082568  76 RTnnwltlqetmLQRLKEGKIESLRQLIYDAGREypRQELVTEVLRPLRSQVSANVPAIMTL 137
Cdd:cd04783   76 SE----------ARELAEQKLAEVDEKIADLQRM--RASLQELVSQCAATKNNVSCPIIAAL 125

Helix-Turn-Helix DNA binding domain of the HspR transcription regulator; Helix-turn-helix (HTH) transcription regulator HspR, N-terminal domain. Heat shock protein regulators (HspR) have been shown to regulate expression of specific regulons in response to high temperature or high osmolarity in Streptomyces and Helicobacter, respectively. These proteins share the N-terminal DNA binding domain with other transcription regulators of the MerR superfamily that promote transcription by reconfiguring the spacer between the -35 and -10 promoter elements. A typical MerR regulator is comprised of distinct domains that harbor the regulatory (effector-binding) site and the active (DNA-binding) site. Their conserved N-terminal domains contain predicted winged HTH motifs that mediate DNA binding, while the dissimilar C-terminal domains bind specific coactivator molecules.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|....*.
gi 496082568   3 YSIGEFARLCGINATTLRAWQRRyGLLKPLRTDGGHRQYSDDDVQQ 48
Cdd:cd04766    2 YVISVAAELSGMHPQTLRLYERL-GLLSPSRTDGGTRRYSERDIER 46

Zn(2+)-responsive transcriptional regulator;

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 496082568   3 YSIGEFARLCGINATTLRAWQRRyGLLKP-LRTDGGHRQYSDDDVQQALKILDWVKKGVPVSQVKPLLS 70
Cdd:PRK09514   2 YRIGELAKLAEVTPDTLRFYEKQ-GLMDPeVRTEGGYRLYTEQDLQRLRFIRRAKQLGFTLEEIRELLS 69

MerR family regulatory protein;

                          10        20        30
                  ....*....|....*....|....*....|....*...
gi 496082568    4 SIGEFARLCGINATTLRAWQRRYGLLKPLRTDGGHRQY 41
Cdd:pfam00376   1 TIGEVAKLLGVSPRTLRYYEKIGLLPPPERTEGGYRRY 38

Helix-Turn-Helix DNA binding domain of the CadR- and PbrR-like transcription regulators; Helix-turn-helix (HTH) CadR- and PbrR-like transcription regulators. CadR and PbrR regulate expression of the cadmium and lead resistance operons, respectively. These proteins are comprised of distinct domains that harbor the regulatory (effector-binding) site and the active (DNA-binding) site. Their conserved N-terminal domains contain predicted winged HTH motifs that mediate DNA binding, while the C-terminal domains have three conserved cysteines which comprise a putative metal binding site. Some members in this group have a histidine-rich C-terminal extension. These proteins share the N-terminal DNA binding domain with other transcription regulators of the MerR superfamily that promote transcription by reconfiguring the spacer between the -35 and -10 promoter elements.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|....*.
gi 496082568   3 YSIGEFARLCGINATTLRAWQRRyGLL-KPLRTDGGHRQYSDDDVQ 47
Cdd:cd04785    1 LSIGELARRTGVNVETIRYYESI-GLLpEPARTAGGYRLYGAAHVE 45

Helix-Turn-Helix DNA binding domain of Heavy Metal Resistance transcription regulators; Helix-turn-helix (HTH) heavy metal resistance transcription regulators (HMRTR): MerR1 (mercury), CueR (copper), CadR (cadmium), PbrR (lead), ZntR (zinc), and other related proteins. These transcription regulators mediate responses to heavy metal stress in eubacteria. They belong to the MerR superfamily of transcription regulators that promote transcription of various stress regulons by reconfiguring the operator sequence located between the -35 and -10 promoter elements. A typical MerR regulator is comprised of two distinct domains that harbor the regulatory (effector-binding) site and the active (DNA-binding) site. Their N-terminal domains are homologous and contain a DNA-binding winged HTH motif, while the C-terminal domains are often dissimilar and bind specific coactivator molecules such as metal ions, drugs, and organic substrates.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|....*..
gi 496082568   3 YSIGEFARLCGINATTLRAWQRRyGLL-KPLRTDGGHRQYSDDDVQQ 48
Cdd:cd04770    1 MKIGELAKAAGVSPDTIRYYERI-GLLpPPQRSENGYRLYGEADLAR 46

Second Helix-Turn-Helix DNA binding domain of the regulatory protein TioE; Putative helix-turn-helix (HTH) regulatory protein, TioE, and related proteins. TioE is part of the thiocoraline gene cluster, which is involved in the biosynthesis of the antitumor thiocoraline from the marine actinomycete, Micromonospora. These proteins share the N-terminal DNA binding domain with other transcription regulators of the MerR superfamily that promote transcription by reconfiguring the spacer between the -35 and -10 promoter elements. Proteins in this family are unique within the MerR superfamily in that they are composed of just two adjacent MerR-like N-terminal domains; this CD mainly contains the C-terminal or second repeat (rpt2) of these tandem MerR-like domain proteins.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 496082568   3 YSIGEFARLCGINATTLRAWQRRyGLLKPLRTDG-GHRQYSDDDVQQALKILDWVKKGVPVSQVKPLL 69
Cdd:cd04773    1 MTIGELAHLLGVPPSTLRHWEKE-GLLSPDREPEtGYRVYDPSDVRDARLIHLLRRGGYLLEQIATVV 67

Helix-Turn-Helix DNA binding domain of the YfmP transcription regulator; Helix-turn-helix (HTH) transcription regulator, YfmP, and related proteins; N-terminal domain. YfmP regulates the multidrug efflux protein, YfmO, and indirectly regulates the expression of the Bacillus subtilis copZA operon encoding a metallochaperone, CopZ, and a CPx-type ATPase efflux protein, CopA. These proteins belong to the MerR superfamily of transcription regulators that promote expression of several stress regulon genes by reconfiguring the spacer between the -35 and -10 promoter elements. Their conserved N-terminal domains contain predicted winged HTH motifs that mediate DNA binding, while the dissimilar C-terminal domains bind specific coactivator molecules.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|.
gi 496082568   3 YSIGEFARLCGINATTLRAWQRRyGLLKPLRTDGGHRQYSDDDVQQALKIL 53
Cdd:cd04774    1 YKVDEVAKRLGLTKRTLKYYEEI-GLVSPERSEGRYRLYSEEDLKRLERIL 50

Helix-Turn-Helix DNA binding domain of HspR-like transcription regulators; Helix-turn-helix (HTH) transcription regulator HspR and related proteins, N-terminal domain. Heat shock protein regulators (HspR) have been shown to regulate expression of specific regulons in response to high temperature or high osmolarity in Streptomyces and Helicobacter, respectively. These proteins share the N-terminal DNA binding domain with other transcription regulators of the MerR superfamily that promote transcription by reconfiguring the spacer between the -35 and -10 promoter elements. A typical MerR regulator is comprised of two distinct domains that harbor the regulatory (effector-binding) site and the active (DNA-binding) site. Their conserved N-terminal domains contain predicted winged HTH motifs that mediate DNA binding, while the dissimilar C-terminal domains bind specific coactivator molecules.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|....*
gi 496082568   3 YSIGEFARLCGINATTLRAWQRrYGLLKPLRTDGGHRQYSDDDVQ 47
Cdd:cd01279    2 YPISVAAELLGIHPQTLRVYDR-LGLVSPARTNGGGRRYSNNDLE 45

Helix-Turn-Helix DNA binding domain of putative transcription regulators from the MerR superfamily; Putative helix-turn-helix (HTH) MerR-like transcription regulators (subgroup 4). Based on sequence similarity, these proteins are predicted to function as transcription regulators that mediate responses to stress in eubacteria. They belong to the MerR superfamily of transcription regulators that promote transcription of various stress regulons by reconfiguring the operator sequence located between the -35 and -10 promoter elements. A typical MerR regulator is comprised of two distinct domains that harbor the regulatory (effector-binding) site and the active (DNA-binding) site. Their N-terminal domains are homologous and contain a DNA-binding winged HTH motif, while the C-terminal domains are often dissimilar and bind specific coactivator molecules such as metal ions, drugs, and organic substrates.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....
gi 496082568   3 YSIGEFARLCGINATTLRAWQRrYGLLKPLRTDGGHRQYSDDDVQQALKILDWVKKGVPVSQVK 66
Cdd:cd04779    1 YRIGQLAHLAGVSKRTIDYYTN-LGLLTPERSDSNYRYYDETALDRLQLIEHLKGQRLSLAEIK 63

Helix-Turn-Helix DNA binding domain of MerR2-like transcription regulators; Helix-turn-helix (HTH) transcription regulator MerR2 and related proteins. MerR2 in Bacillus cereus RC607 regulates resistance to organomercurials. The MerR family transcription regulators have been shown to mediate responses to stress including exposure to heavy metals, drugs, or oxygen radicals in eubacterial and some archaeal species. They regulate transcription by reconfiguring the spacer between the -35 and -10 promoter elements. A typical MerR regulator is comprised of two distinct domains that harbor the regulatory (effector-binding) site and the active (DNA-binding) site. Their N-terminal domains are homologous and contain a DNA-binding winged HTH motif, while the C-terminal domains are often dissimilar and bind specific coactivator molecules such as metal ions, drugs, and organic substrates.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 496082568   5 IGEFARLCGINATTLRAWQRRyGLLKPLRTDGGHRQYSDDDVQQALKILDWVKKGVPVSQVKPLLSRPGARRTNNWLTLQ 84
Cdd:cd04769    3 IGELAQQTGVTIKAIRLYEEK-GLLPSPKRSGNYRVYDAQHVECLRFIKEARQLGFTLAELKAIFAGHEGRAVLPWPHLQ 81

                         90       100
                 ....*....|....*....|.
gi 496082568  85 EtMLQRLKE---GKIESLRQL 102
Cdd:cd04769   82 Q-ALEDKKQeirAQITELQQL 101

Helix-Turn-Helix DNA binding domain of the Cfa transcription regulator; Putative helix-turn-helix (HTH) MerR-like transcription regulator; the N-terminal domain of Cfa, a cyclopropane fatty acid synthase and other related methyltransferases. Based on sequence similarity, these proteins are predicted to function as transcription regulators that mediate responses to stress in eubacteria. They belong to the MerR superfamily of transcription regulators that promote transcription of various stress regulons by reconfiguring the operator sequence located between the -35 and -10 promoter elements. A typical MerR regulator is comprised of distinct domains that harbor the regulatory (effector-binding) site and the active (DNA-binding) site. Their N-terminal domains are homologous and contain a DNA-binding winged HTH motif, while the C-terminal domains are often dissimilar and bind specific coactivator molecules such as metal ions, drugs, and organic substrates.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|
gi 496082568   3 YSIGEFARLCGINATTLRAWQRRyGLLKPLRTDGGHRQYSDDDVQQALKI 52
Cdd:cd04789    2 YTISELAEKAGISRSTLLYYEKL-GLITGTRNANGYRLYPDSDLQRLLLI 50

Helix-Turn-Helix DNA binding domain of putative transcription regulators from the MerR superfamily; Putative helix-turn-helix (HTH) MerR-like transcription regulators (subgroup 6) with at least two conserved cysteines present in the C-terminal portion of the protein. Based on sequence similarity, these proteins are predicted to function as transcription regulators that mediate responses to stress in eubacteria. They belong to the MerR superfamily of transcription regulators that promote transcription of various stress regulons by reconfiguring the operator sequence located between the -35 and -10 promoter elements. A typical MerR regulator is comprised of two distinct domains that harbor the regulatory (effector-binding) site and the active (DNA-binding) site. Their N-terminal domains are homologous and contain a DNA-binding winged HTH motif, while the C-terminal domains are often dissimilar and bind specific coactivator molecules such as metal ions, drugs, and organic substrates.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|....*
gi 496082568   4 SIGEFARLCGINATTLRAWQRRyGLLKPLRTDGGHRQYSDDDVQQ 48
Cdd:cd04781    2 DIAEVARQSGLPASTLRYYEEK-GLIASIGRRGLRRQYDPQVLDR 45